19 research outputs found
Solvent and Substituent Effects on the Aggregation Behavior of Surface-Active Ionic Liquids with Aromatic Counterions and the Dispersion of Carbon Nanotubes in their Hexagonal Liquid Crystalline Phase
The
aggregation behavior of surface-active ionic liquids (SAILs)
1-dodecyl-3-methylimidazolium <i>m</i>- and <i>p</i>-hydroxybenzoate (<i>m</i>-C<sub>12</sub>mimHB and <i>p</i>-C<sub>12</sub>mimHB) in water and ethylammonium nitrate
(EAN) was investigated. Surface tension measurements indicate that
the cmc values of SAILs in EAN are much higher than those in water,
resulting from the weaker solvophobic effect of EAN, and the stronger
stability of SAILs/EAN complexes proven by DFT calculations. Compared
to 1-dodecyl-3-methylimidazolium salicylate (C<sub>12</sub>mimSal),
the effect of substituent position leads to weaker interactions between
aromatic counterions and headgroups. The hexagonal liquid crystal
(H<sub>1</sub>) phase formed by C<sub>12</sub>mimHB in water or EAN
at a higher concentration was determined by polarized optical microscopy
(POM), small-angle X-ray scattering (SAXS), and rheology techniques.
Structural parameters estimated from SAXS curves suggest that the
higher SAILs concentration or temperature leads to a smaller lattice
parameter (<i>a</i><sub>0</sub>) and a denser arrangement
of cylinders. For C<sub>12</sub>mimHB, the formation of the H<sub>1</sub> phase in H<sub>2</sub>O is easier than that in EAN. Furthermore,
compared to C<sub>12</sub>mimSal, C<sub>12</sub>mimHB exists over
a broad region of the hexagonal liquid crystalline (H<sub>1</sub>)
phase, which is due to the different position of the substituents
on the aromatic ring of counterions. Therefore, the H<sub>1</sub> phase
of the lypotropic liquid crystals (LLCs) formed in the C<sub>12</sub>mimHB/H<sub>2</sub>O system exhibits excellent performance in uniformly
dispersing multiwalled carbon nanotubes (MWCNTs). Increasing the concentration
of MWCNTs results in a larger lattice parameter (<i>a</i><sub>0</sub>) value, indicating the integration of MWCNTs within
the cylinders of the H<sub>1</sub> phase. The rheological measurement
results demonstrate that MWCNTs/LLCs composites are highly viscoelastic,
and the presence of MWCNTs obviously strengthens the apparent viscosity
of the H<sub>1</sub> phase
Rapid and Efficient Functionalized Ionic Liquid-Catalyzed Aldol Condensation Reactions Associated with Microwave Irradiation
Five quaternary ammonium ionic liquid (IL) and two tetrabutylphosphonium ILs were prepared and characterized. An environmentally benign and convenient functionalized ionic liquid catalytic system was thus explored in the aldol condensation reactions of aromatic aldehydes with acetone. The aldol reactions proceeded more efficiently through microwave-assisted heating than through conventional thermal heating. The yield of products obtained under microwave heating for 30 min was approximately 90%, and the ILs can be recovered and reused at least five times without apparent loss of activity. In addition, this catalytic system can be successfully extended to the Henry reactions